This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. We are also interested in cofactor biosynthesis. We are currently focusing our efforts in this area on thiamin and pyridoxal 5'-phosphate (PLP) biosynthesis. Many of the reactions catalyzed by the enzymes in thiamin biosynthesis involve unprecedented chemistry and elucidation of catalytic mechanism is a major goal. By studying these enzymes, we have also discovered interesting evolutionary links to other pathways. PLP is the biologically active form of vitamin B6 and is an important cofactor for several of the enzymes involved in the metabolism of amine-containing natural products such as amino acids and amino-sugars. Of particular evolutionary interest is the finding that there are two distinct PLP biosynthetic pathways that have not yet been found to coexist in the same organism